This invention relates in general to well pumps, and in particular to a restrictor device that restricts entry of gas into the intake of a horizontally oriented pump.
Submersible well pumps are frequently employed for pumping well fluid from lower pressure oil wells. One type of pump comprises a centrifugal pump that is driven by a submersible electrical motor. The pump has a large number of stages, each stage comprising a diffuser and an impeller. Another type of pump, called progressive cavity pump, rotates a helical rotor within an elastomeric helical stator. In both types, the motor for driving the pump is typically an electrical motor submerged with the pump. Centrifugal pumps are normally used for pumping higher volumes of well fluid than progressive cavity pumps.
Both types of pumps become less efficient when significant amounts of gas from the well fluid flow into the intakes. Any gas in the well fluid tends to flow upward to the higher side of the casing. A pocket of free gas may form in the upper portion of the horizontal casing. The free gas tends to flow into the portion of the intake on the higher side of the pump.
The pump intake of this invention has a tubular housing with a plurality of apertures for receiving well fluid. The apertures are spaced circumferentially around the housing. Once installed in a horizontal portion of the well, the pump will be located on a lower side of the well casing. At least one of the apertures will be located at a higher elevation than the other apertures. The higher elevation aperture would be exposed to well fluid that has a higher gas content, or it may be entirely gas. The lower elevation aperture would be exposed to higher liquid content of well fluid.
A restrictor is located within the housing for partially blocking the higher elevation aperture. The restrictor also opens the lower elevation aperture to allow liquid to flow into the lower elevation aperture. The partial blocking of the higher elevation aperture restricts the entry of gas into the intake assembly housing.
The restrictor automatically moves into a position blocking the higher elevation aperture during installation of the pump. In the first embodiment, the restrictor is buoyant in the well fluid. The buoyancy causes the restrictor to rise from a lower side of the intake assembly to an upper side at least partially blocking the higher elevation aperture and freeing the lower aperture from blockage.
In the second and third embodiments, the restrictor moves out of engagement with the lower elevation aperture in response to the housing coming into contact with the lower wall of the well casing. This movement is handled by one or more pins that protrude through holes in the housing. The restrictor is flexible, and when a pin contacts the lower side of the casing, it flexes a portion of the restrictor upward to open the lower aperture for receiving well fluid. The upper aperture remains blocked due to a bias of the restrictor against the sidewall of the housing.